This invention relates to a method and apparatus for the noninvasive analysis of joint disorders. More particularly, this invention relates to a new and improved noninvasive technique for detecting and analyzing joint disorders which utilizes a novel signal processing procedure termed Arthrophonometry. This invention is particularly well suited for the detection and differential diagnosis of temporomandibular joint (TMJ) disorders, a prevalent class of disorders caused by any of a number of different underlying pathologies.
It is well known that from a mechanical point of view, there are four classes of joints in the human body including: (1) Ginglymal or hinge (e.g. knee, elbow, digits); (2) Arthrodial or gliding (e.g. wrist); (3) Spheroid or ball-and-socket (e.g. shoulder, hip); and (4) Ginglymo--arthrodial or hinge-and-gliding (e.g. temporomandibular (TMJ)). Of these four classes, only the ginglymal or hinge joints such as the knee may be described positionally by using joint angle (e.g. a two-dimensional measurement). The other three classes of joint cannot be described positionally by joint-angle; but must be characterized in a three-dimensional coordinate system that uses lineal displacement measurements. As will be discussed in further detail hereinafter, the present invention quantitates joint position in three-dimensional space. Hence, the present invention is a technique for use with joints of the arthrodial, spheroid and ginglymo-arthrodial classes; and is not applicable to ginglymal joints such as the knee and elbow.
While the present invention may be used in conjunction with arthrodial, spheroid and ginglymo-arthrodial joint types, it is particularly well suited as a technique for the detection and differential diagnosis of temporomandibular joint disorders. Thus, it should be understood that while the following discussion of the present invention and the relevant background thereof relates primarily to the diagnosis of temporomandibular (TMJ) and related joint disorders, the present invention is equally applicable to the diagnosis of other types of joint disorders which involve arthrodial, spheroid and ginglymo-arthrodial types of joints.
Pain and dysfunction associated with the TMJ are estimated to afflict 20%-50% of the population. Most patients probably have functional disorders, but organic joint disease is undoubtedly present in a certain percentage thereof. Unfortunately, differentiating true joint pathology from other conditions can be difficult or impossible due to the relatively non-specific nature of the relevant clinical signs and symptoms. Moreover, recognition of an increasing number of different types of joint abnormalities has caused the need for simple, objective, and definitive diagnostic methods to assume greater importance. Conditions such as myofascial pain dysfunction (MPD), meniscal displacements (internal derangements), rheumatic and degenerative arthritis, subluxation and chronic dislocation, fractures, tumors, and ankylosis are all recognized as distinct entities, but their diagnosis has generally relied on clinical impression and complex radiographic methods. The prevalent tendency to perceive TMJ disease as MPD may have evolved from inadequate diagnostic techniques and an inability to distinguish specific disease entities on the basis of objective criteria. An increasing repertory of effective surgical and non-surgical treatments for specific joint abnormalities necessitates a greater degree of diagnostic accuracy.
Aside from direct clinical examination, the most common TMJ diagnostic techniques rely on radiography. Historically, radiographic evidence of TMJ change has been considered the hallmark for differentiating organic joint diseases from functional disorders. Radiographic assessment of the TMJ is generally confined to standard radiography, arthrography, tomography, and arthrotomography. While standard radiography and tomography are useful in evaluating gross abnormalities of osseous structures, they have little value in assessing the viability and function of soft tissue components. Not surprisingly, tomograms are completely normal in 86%-95% of patients with TMJ dysfunction. Since impressive evidence has now verified the significance of soft tissue derangements in TMJ dysfunction, the serious limitations of standard radiography and tomography have become apparent. Even for assessing the normalcy of osseous structures, the value of standard techniques has been shown to be limited and to require substantial radiation exposure.
Improved, yet nevertheless deficient, procedures for objectively studying the soft tissue function of the TMJ have been found in simple arthrographic methods. Still better data results from combining arthrography with tomography (i.e., arthrotomography). Although this technique allows definitive identification of anterior meniscal dislocations and subluxations, meniscal perforations, degenerative changes, and adhesions, substantial specialized skill in interpreting resulting arthrotomograms is required. Difficulties in the unambiguous interpretation of such films continue to limit the value of arthrotomography as a routine technique.
Undeniably, arthrotomography has permitted diagnosis of certain TMJ abnormalities with unprecedented reliability, but the technique should be viewed as invasive. As a tomographic method (othen performed under fluoroscopic control), patients are necessarily subjected to significant levels of radiation. The need to expose patients to a potentially allergenic iodine-containing contrast medium and to considerable pain has generally been balanced by the valuable diagnostic information obtained; but, these inherent disadvantages in arthrotomography emphasize the potential value of a quantitative, non-invasive, non-radiographic technique that should provide as much or more information as that available through existing methods.
Finally, computed tomography (CT) of the TMJ has been described as an alternative to conventional tomography and arthrotomography. CT offers increased sensitivity and reliability for studying both hard and soft tissues while exposing the patient to less radiation and pain than other radiographic methods. Nonetheless, CT scan of the TMJ is a hospital procedure requiring expensive equipment and facilities, specially-trained physicians, and moderate radiation dosages. The design of a suitable quantitative, non-invasive TMJ diagnosis procedure which overcomes the above discussed problems may be effected in light of two related premises: (1) that an abnormal joint will exhibit frictional losses that are different than those of a normal joint and which can easily be detected instrumentally, and; (2) different pathologies will present different types of frictional losses which can be identified and quantified acoustically.
Certain noninvasive acoustical evaluation techniques are well known in the medical diagnostic art. For example, in U.S. Pat. No. 3,181,528 to Brackin, a method and apparatus is disclosed for analyzing joint disorders utilizing acoustical diagnostic equipment to detect joint emitted sounds. Brackin teaches that there is a unique acoustic pattern of signature underlying those sounds recorded from different pathologies. In order to determine the characteristics of that signature, Brackin performs a complex analysis (Fast Fourier Transform) of the noises produced by a normal joint and the suspected joint and compares the differences between the two joints. Brackin specifically teaches against joint angle recording (Column 4, lines 63-71), claiming that the presumed acoustic fingerprint is the only salient diagnostic parameter. Brackin also teaches that it is important for the patient to be able to produce joint movements rhythmically, but without any constraints imposed by a device attached to the bones that would regulate or impede those movements mechanically. Thus, Brackin's device also incorporates a timer (actually a metronome), the movements of which the patient observes in an attempt to keep flexion and extension "in time" (column 5, lines 1-14). It is important to emphasize the point that this timer is used only to rhythmically regulate limb movements, there is no disclosure or suggestion by Brackin concerning the measurement or correlation of joint sounds with either joint angle or time.
U.S. Pat. No. 4,437,473 to Mollan discloses a method which is similar to Brackin with two exceptions. Mollan teaches the importance of recording subsonic frequencies, and Mollan also discloses a record of joint noise vs. joint angle (FIG. 2). Like Brackin's method, Mollan's technique also explicitly seeks a unique acoustic signature for each individual type of pathology and requires a comparison between normal and pathological joint noises in order to detect the pathology (column 3, lines 64-68; column 4, lines 1-4). Although in one example, reference to the angle of the joint is made, the criterion measure for the diagnosis is the nature of the emitted sound pattern, not the angle position of the joint (column 4, lines 16-22). No demonstrations or documentation of joint angle position is provided by Mollan. Significantly, the duration of the movement, and the correlation of the duration of the movement with the angle of the joint and the appearance of the sound is not disclosed.
In an article in the Medical & Biological Engineering & Computing magazine entitled "A Noninvasive Electroacoustical Evaluation Technique of Cartilage Damage in Pathological Knee Joints", the authors therein describe a technique similar to the Brackin patent wherein knee joint disorders are diagnosed by measuring and recording the emission of a unique acoustical signature and the corresponding statistical pattern. As in Brackin, this technique obtains graphic results measuring the sound waveform or sound spectras. A further diagnostic device, similar to the aforementioned joint noise detecting systems is described in Russian Pat. No. 304939.
Unfortunately, all of the above procedures and apparatii suffer critical deficiencies in the degree of quantitative analysis and diagnostic accuracy. Accordingly, these prior art procedures find only limited acceptance chiefly due to their merely qualitative approach to diagnosis of specific disorders.
Accordingly, it would be advantageous to provide a noninvasive acoustical diagnostic tool for the accurate, quantitative detection and differential diagnosis of joint disorders, particularly TMJ disorders.